1. Field
The following description relates to synchronization in a super regenerative receiver (SRR).
2. Description of Related Art
A super regenerative receiver (SRR) is a low-power receiver that may be used in wireless sensor networks. In wireless sensor networks, for example, license-free industrial, scientific, and medical radio (ISM) bands, many nodes co-exist in the same frequency band. However, such SRR-based communication nodes are affected by interference due to lower adjacent channel interference (ACI) and alternate channel interference (ALCI) rejection capabilities of the SRR.
In typical super-heterodyne or direct conversion receivers, passband signals are down-converted to an intermediate frequency or a baseband frequency using mixers and filtered in a baseband to improve an interference rejection capability. However, using a filter in an SRR has an undesirable effect on power consumption because the SRR operates at a radio frequency (RF). Moreover, there is no distinction in an output of the SRR depending on whether an input of the SRR is at a resonant frequency or at some frequency offset from the resonant frequency, which prevents an application of filtering techniques at the output of the SRR.
Another approach for to improve the interference rejection capability of the SRR uses undersampling (for example, sampling at less than 2 times a chip rate) of a signal to improve the interference rejection capability. However, the undersampling of the signal may disturb synchronization of the SRR. Furthermore, sampling of the received signal at a rate corresponding to 1.5 times the chip rate or any fractional sampling may impose certain challenges in terms of synchronization. The fractional quench rate of 1.5 times the chip rate will provide a fractional number (1.5) of samples per each chip, which indicates that, for every two chips, three samples will be available at a receiver baseband. A possible number of sets of two samples out of three samples that may represent the two chips is 3 or
      (                            3                                      2                      )    .In these three samples, there are two samples that best represent the two chips, which is a desired sample set. Identification of the desired sample set from all three possible sample sets is performed by pulse synchronization.